Method for making impressions of objects



Nov. 22, 1949' w. J. MEAD METHOD FOR MAKING IMPRESSIONS OF OBJECTS 2 Sheets-Sheet 1 Filed Sept. 20, 1944 Nov. 22, 1949 w. J. MEAD METHOD FOR MAKING IMPRESSIONS OF OBJECTS Filed Sept. 20, 1944 2 Sheets-Sheet 2 mani Warn??? J Head Patented Nov. 22, 1949 "METHGD -FOR MAKING IMPRESSIONS OF OBJECTS W arren J ,Mead, BelmontrMass.

Application September 20, 1944, Serial No.555,01'0

2 Claims. (01. 18:55.05)

1 This invention relates :touthe uart v..or.:methodof making moulds :or impressions of the complete or-partial form of objects.

The invention provides .a novel mode of' making a-quick, accurate impressionor mould of ;anobject whose .form it is desired-to reproduce, from which impression alcasting may bemade ofsuitable materiaLsuch as plaster or wax, ora pattern or replica of an object maybe-made from a. mould and used in making othermoulds.

To practice the invention theprocedure to be followed may be briefly and in :general terms stated thus: the object, an impressionof which is desired, and a thin, flexible andextensible :Wall of an impervious container enclosing a-deformablemass of -mixed granular material and =fluid, are pressed into contactone withthe other, so that the flexiblewalland its underlying mass of granular material andfluid conform to the shape of the surface of the object. The-granularmass in its thus conformed shape is then-solidified by reducing the pressure ,of the fluid.

There are two-exemplifications of the procedure, similar in principle, for carrying out the invention, one suitable for 'obtainingan impression or mould of an exterior-surface of'theobject,.and the other suitable for obtaining an impression of an interior .surface of an enclosed cavity.

If an impression of an exterior surface is de-- sired, theobject is pressed against andinto a thin, flexible, extensible wall of an impervious container enclosing a deformable mass of mixed granular material and fluid so as to force'the wall into the underlying mass, .thereby'to-form an impression of the shape of the object, and then, while the impression is maintained by-"the presence of the object, the pressure of the 'fluid is reduced sufficiently to solidify the granular mass. When the object is withdrawn the impression persists as long as the low pressure within the container is maintained, and a casting may be made of the impression, therebyproducing a facsimile of the shape of the object which'has been pressed into the wall of the container. bviously the same result would be obtained "by pressing the container wall againsttheobject as by pressing the object againstthe container wall.

If an impression is desired of the interior surface of an enclosed cavity (closed excepting for an inlet passage), such as that of a two-part or multiple part mould used in foundry work,a sack made of sheet rubber or other suitableflexible and extensible material is inserted into thecavity forms with :the interior .surface {of time mould. Into this .infiated .sack :fine :sand or .;other .f ranulated material is introducedand shakentortvir brated so that incompletely fills .tthe .sackland is in .a I conditionapproaching 1 dense or :close :packing. The :fiuid 1(liquid .or .gas) is {then partially evacuated from the .sack .and the .sack is :sealed, the plaster mould .opened, :and the :rigid, sand filledtsackrbecomes a pattern aboutwhicha sand mould, or similar typelof-mould, can bexbuilteand consolidated, after which :theneck f .the sack is opened,.=the sand poured out, and:the-rubbersack withdrawn. :This operation may berepeatedsindefinitely to produce multiple moulds.

The principle of the solidification of an enclosed granular mass by reducing-the; pressure of fluid mixed with it is related-to the I phenomenon known I as dilatancy, -which is the property of granular -masses to expand in bulk with change of -shape-dueto-the increaseof--space*between-the individually rigid 1 particles as they change their relativeposition. If a granular mass in a condition of close packing is closely conflnedin a flexible, closed and 'impervionslenvelope, it will be found that it resists deformation to an astcng ishing degree because when deformed it must increase in volume and requires-more fluid thanis available to fill the increased volume of voids. Fluid pressure --within the container tends to be reduced by any tendency to change the shape of themass, and atmosphericpresSMeforces the envelope tightly about the-'mass preventing dilation, increasing inter-granular friction, and induci risidity.

'Similarly if, instead of being closely packed, the granules are; mixed with acopiousvolumeof fluid, liquid or gaseous, so that-theinixtuije will be capable of being "deformed or of yielding sufficiently to receive an impression conforming to the shape of the object against which fit is pressed, and if then ,the pressure of the fluid 'is reduced whilethe impression of-' the object isjretained bythe presence of the object, the granular mass will become solid or rigi d, and will retain the impression so long as the negative pressure is maintained.

The sranuianm e i ma h m n Suitabl particle size, which size may vary from that of very fine sand to that of coarse sand. ,'I he;fi nr the granules the more faithfully wi ll'details of the form 'of'the object to be reproduced Iappear in'the impression. i'lhe granules need notbei of uniformsize or of uniform shape; they maybe 0111 0 an u r 'i flfi ul n sh of the two-part mould and inflated so that it con- The granular material may be any organic or such as sheet rubber in the form of a sack, en-

velope or balloon. Or it may have a rigid body, of metal or plastic for example, or other air-tight and water-tight material having an opening at one side which is closed with a cover or wall formed of the flexible, impervious sheet material sealed over the openingto receive the impression. The important condition is that at least one wall or the container be made of a sheet of flexible and extensible material to receive the impression and that the container as a whole be substantially impervious to air or water. The container should be provided with an openmg or openings at which tubes or pipes may be connected through which fluid may be introduced and withdrawn. The fluid may be introduced into thecontainer by any suitable means, and may be withdrawn from the container to reduce the fluid pressure by any suitable form of exhaust pumping device. The outlet to the exhaust line is preferably screened to prevent the escape of granular material while permitting the passage of the fluid.

The fluid may be liquid or gaseous, for example water or air, and is introduced into and mixed with the granular mass in such quantity as to loosen the grains and render the whole mixture sufliciently fluid or mobile to receive the impression of the object whose shape is to be reproduced. I I

By way of illustration, but not of limitation, certain embodiments of devices and apparatus for practicing the method are shown in diagrammatic or schematic form in the accompanying drawings, in which 1 is a schematic representation of simple equipment formaking impressions of an exterior surface of an object;

Fig. 2 illustrates an arrangement employing a valve-less piston pump;

Fig. 3 illustrates an arrangement employing a metal bellows pump of the Sylphon type;

Fig. 4 represents a container whose walls other than the wall to receive the impression are rigid;

Fig. 5 illustrates an adaptation of the invention to the making of a completely encircling impression of a withdrawable object;

Fig. 6 represents the application of the invention to the making of a pattern of the interior surface of an enclosed mould or cavity; and Fig. 6 illustrates one of the steps in moulding a pattern according to the procedure of Fig. 6.

Referring to Fig. l a container is shown in the form ofa sack or balloon I of rubber or other suitable thin, impervious, tough, extensible, elastic material. Tightly fitted into the neck 2 of the container is a perforated rubber stopper or plug 3, into which is sealed a tube 4 having at its inner end a screen to prevent escape of the granular material and to permit the free passage of fluid in or out of the container. To the outer end of tube 4 a pipe 6 is connected leading to a three-way cock I. Connected to the three-way cock are also a fluid inlet pipe 8 and a fluid outlet or exhaust pipe 9. The container 1 is filled with sand or other suitable granular material and is externally exposed to the pressure of the ambient atmosphere. To make an impression or mould of an object the cock 1 is turned to open the inlet pipe 8 and connect it to the pipe 6 and to close the exhaust pipe 9. Sufficient fluid, liquid or gas, is introduced through inlet pipe8 from any suitable source of supply'under pressure to render the granular material Ill within the container l deformable. The object, of which an impression is to be taken, is pressed into the upper side of the container I and at the same time, if necessary, suflicient additional fluid may be introduced through the inlet 8 to permit desirable seating of the object. When the desired seating and impression of the object are obtained the cock 1 is turned to close the inlet passage 8 and connect pipe 6 to the exhaust passage 9, which leads to a suction device. Suction is then applied to the exhaust line 9 until a sufficient degree of negative pressure (that is to say, a pressure less than that of the fluid medium i. e. atmospheric air, which contacts the external surface of the container) is reached to cause the container l and its enclosed granular material to become rigid. The object is then removed. While suction is still maintained, or while the reduced pressure of the fluid within the container is maintained by turning the cock to close both passages 8 and 9, a cast of the impression may be made with plaster or other suitable material.

Instead of using separate devices for the introduction and extraction of fluid, controlled by a suitable valve arrangement as illustrated in Fig. 1, I have found that, since extremely low pressures in the container are not required for either gas or liquid, it is possible to use Very simple devices by which both the introduction and extraction of fluid are accomplished by the same device.

Fig. 2 illustrates a valve-less piston-pump connected to the container. When the handle H of the piston I2 is pressed down it forces fluid from the cylinder 13 into the granular filled container 1. When the pressure at l I is released the spring 14 surrounding the piston rod draws the piston upwardly and reduces fluid pressure in the container, causing the contained granular mass to become rigid.

Another valve-less device is illustrated in Fig. 3, which shows metal bellows i5 of the Sylphon type connected through a pipe to the container 6. A spring it normally urges the bellows toward an expanded position. When the bellows and spring are compressed fluid is forced from the bellows into the container. When the bellows and spring are released the increased volume of the bellows produced by the extension of the bellows developed by the spring produces a sufficiently low pressure in the container to cause adequate solidification of the granular material. This form of device is usually suitable for use only with a relatively small container.

Fig. 4 illustrates still another form of container consisting of animpervious vessel is made of metal, plastic or other suitable rigid material, open at the top side, The opening is covered by a sheet of flexible, elastic material l9 such as rubber. The cover sheet i9 is sealed across the open side of the container 18, as by cement and a band I! tied under a beaded edge of the container vessel It. The object, of which a mould is desired, is pressed into the sheet and with the sheet into the underlyin-g agranular material 10.

-A sma'llspace ispreferably left between thesheet and the normal level of the granular material to permit the rise of displaced granules when the object is inserted. An inlet .zpi-pe 20 is provided -for introducing fluid to loosen the granular material and render it deformable, and an exhaust pipe 2| leads =t'a suction device by'which fluid may be withdrawn and the mould thereby consolidated.

An adaptation of the invention to the making of a completely encircling impression of an object which is so shaped as to be capable of being withdrawn after the .granularmass has become rigid is illustratedin Fig. 5. Specifically, the object-22 shown-in Fig. 5, may be'the stump of an amputated leg. 23 represents a tubular casing, which is preferably conical ortapered in shape, made of metal'onothersuitablematerial. Within thecasing 23 is a-lining or tubular wall 24 of sheet rubber or other suitable flexible, elastic, impervious material. The wall 2-4 is sealed to the lower end of the casing 23, as'by folding it around the lower end of the casing and .tightly tying it by means of an encircling cord or band 25 above the beaded endof 'th'eca'sing. Granular material H), such as sand, is introduced into the annular space between the wall 24 and the cas- '-ing 23 and the upper end of the tubular wall 2 3 is then folded down over the-topend of the casing as indicated at 24' and sealed-to the casing by tying it bya cord or band 26 underneath the beaded top end of casing, thus forminga closed annular container filled with a-deformable mass of mixed granular material and air, or other fiui'd if desired. The object 22,.such as the stump of an amputated leg, is then pressed down into the bore of the device while the granular mass is deformable and makes its impression in the flexible wall 2 3 and the surrounding granular mass l0. While the object is still in position air (or other fluid if other fluid is used) is exhausted by any suitable means through suction pipe 21 and the granular mass becomes rigid. The object is then withdrawn leaving the impression of its shape, excepting the shape of its lower end. Casts may be made from this impression and used for forming sockets of artificial legs. An advantage of this method of makin a cast, from which a socket of an artificial limb is fashioned, as compared with the usual method of making impressions by means of plaster or the like is that any desired amount of pressure may be exerted by the stump when the impression is taken, in contrast to a passive impression by the usual methods, The resulting socket for an artificial limb therefore fits the stump under conditions of normal load. The end of the stump 22 is left free, as indicated, since an artificial leg is usually supported by the tapering sides of the stump and not by the end which is tender or sensitive.

Instead of a conical casing 23 a cylindrical or other non-tapering form of casing might be used, in which case the mass of granular material for use with a tapering or withdrawable object would be thicker at the lower end of the device and would diminish in thickness toward the top.

Fig. 6 illustrates the use of the invention in the making of a pattern of the interior surface of an enclosed mould or cavity. In foundry work it is sometimes desired to produce multiple sand moulds of an irregular flask-shaped object. From a pattern of the object a plaster mould is first made. The mould is cut so that it may be separated and reassembled. Into the :air rfilled cavity of this plaster mould, consisting of the assembled two parts 28 and 19, :a rubber sack -39 is inserted and inflated so that it conforms with the interior surface 3! of the mould the air initially filling the cavity readily escaping at the parting of the mould. Into this inflated sack fine sand or other granular material it is introduced (Fig. 6 for example, it may be supplied from a reservoir B through a valved conduit P and shaken or vibrated so that it completely fills the sack and is in a condition approaching close packing. The sack is then exacuated through pipe 32 and sealed, as by'tying its neck 33, the plaster mould opened, and the rigid sand-filled sack becomes a pattern about which a sand mould, or similar type of mould, can be built, after which the neck of the sack is opened, the sand poured out and the rubber sack withdrawn.

Obviously the size and shape of the-container may be varied almost indefinitely and adapted to the size and shape of the object whose impression is desired; and the devices for introducing and withdrawing the fluid may be-of many forms and may be hand operated'or mechanically operated, as appears most appropriate or convenient to the work in hand.

A two-part mould may be made'by using two containers filled with granular material, one below and one above the object. The procedure of forming the impressions of the object is substantially the same as already described. If desired the upper container may be mechanically lifted and returned to its original position by any suitable lifting device. A cast is obtained by filling the assembled two-part mould with plaster or other suitable casting material after the object has been removed from the mould sections.

The invention lends itself to a great variety of useful purposes.

One of the important uses of this means of obtaining impressions and thereby casts, is in the making of impressions of the stumps of amputated legs or arms.

Another application is in connection with making impressions of the human foot for orthopedic purposes. Here the shape of the foot under load obtainable by this method has an advantage over a passive impression.

Casts of the head or face or any part of the body can be made by using suitable sized fiat containers which can be easily applied and properly adjusted, solidified and removed quickly and with a minimum of discomfort.

The invention also has useful applications in connection with dental prosthetics. By using a very thin walled container with fine granular material an impression of the gums can be made and any desirable amount of pressure by the gums can be exerted when the impression is obtained.

Individual grips for tools, guns, golf clubs and other articles which it is desirable to have conform to the hand of a particular user may be quickly and accurately made from the impression of the users hand made by grasping a suitably sized cylindrical container.

In art work Or archeology the possible applications of the invention are obvious for reproducing forms or inscriptions.

In connection with mechanical operations the invention may be used to obtain quick impressions of certain types of machine parts. And in science the invention may well be used in making impressions of any solid object, either in the 7 laboratory or in the field by means of a portable outfit.

Other applications will immediately occur to one desiring to obtain a quick and accurate impression of almost any object.

An important advantage of this method of making impressions is that it can be done very quickly and without the application of moisture, liquid, grease or other material or matter to the object to be reproduced.

I claim:

1. That method of making an accurate cast of the peripheral surface of the stump of the amputated leg of a living person while said stump is sustaining approximately one-half of the weight of the person, said method comprising as steps, providing a receptacle having a flexible, vertically elongate tubular inner wall, open at its upper end and which defines a deformable socket which tapers downwardly in diameter and which is of such normal dimensions as to permit the stump to be introduced into it, said receptacle containing fluid and a mass of granular material which contacts the outer surface of said flexible, tubular inner wall, pushing the stump down into said socket and into contact with the inner surface of said tubular inner wall and sustaining approximatel one-half of the persons weight upon the stump b the contact of the peripheral surface of the stump with the flexible wall which defines the socket whereby said fiexible wall is conformed accurately to the contour of said peripheral surface, while the latter is under normal load, solidifying the granular material by reducing the fluid pressure within the receptacle, withdrawing the stump from the socket while maintaining the reduced pressure within the receptacle, and, while still maintaining such reduced pressure, forming a cast of the socket-defining wall.

2. A device for use in the practice of the method of claim 1 comprising a vertical, elongate tubular rigid'casing open at the top, a thin flexible tubular elastic lining within the casing, the upper and lower edges of the lining being secured fluid-tight to the casing, the annular space between the casing and lining containing fluid and a mass of granular material, the inner diameter of the lining being such as to admit the stump of an amputated leg, the linin and granular material which contacts it assuming the contour of the peripheral surface of the stump when the latter is forced down into the tubular lining under the weight of the body, and means operative to reduce'the fluid pressure within said annular space thereby to solidify the granular mass.

WARREN J. MEAD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 20,460 Jeffery Aug. 3, 1937 143,384 Semple Sept. 30, 1873 ,047,594 Trump Dec. 17, 1912 1,154,255 Landis Sept. 21, 1915 1,801,346 Heath Apr. 21, 1931 1,856,394 Lettermann May 3, 1932 2,057,039 MacDonald Oct. 13, 1936 2,145,941 Maxfield Feb. 7, 1937 2,277,288 Berch Mar. 24, 1942 2,280,074 Halsall Apr. 21, 1942 

